A 168kD epithelial molecule, localized to basement membranes, has been identified. Sera from a subset of patients with cicatricial pemphigoid detected the antigen originally. Evidence suggests the antigen is distinct, and not previously characterized. The goal of this proposal is to elucidate the protein and gene structure for this antigen that is enriched in oral epithelium. An existing antibody will be affinity purified, then used to immunopurify the antigen for microsequencing. Expression cDNA libraries will be screened to identify clones encoding the 168kD protein. These will be extended to RACE to obtain the complete coding sequence. From there, fusion protein will be used to obtain further specific antibodies, as a prelude to cell biological and genetic approaches to elucidate the function of the molecule.